How Do I Figure Oz.?????

[Arielluria]

I was told that I can substitute a yarn in a pattern and feel safe it will turn out well if it's the same weight. I assume that's ounces????????

OK. so I'm looking to make the fisherman's sweater (Here's my original post: http://www.knittinghelp.com/knitting...ic.php?t=25873 with pics). Lionbrand's site says fisherman's is 8 oz. But I'm thinking of doing it with Kool Wool which is supposed to be chuncky, then how come on Smiley's Yarn's page it says it's "1 3/4 ounces (50 Grams)" (see sales page). Does that mean they are smaller skeins?

HOW does one know (for online shopping - if you aren't familiar with the yarn) whether the yarn is the same thickness?